Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
  • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
  • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
  • C09C1/0015—Pigments exhibiting interference colours, e.g. transparent platelets of appropriate thinness or flaky substrates, e.g. mica, bearing appropriate thin transparent coatings
  • C09C1/0021—Pigments exhibiting interference colours, e.g. transparent platelets of appropriate thinness or flaky substrates, e.g. mica, bearing appropriate thin transparent coatings comprising a core coated with only one layer having a high or low refractive index
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
  • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
  • C09C1/0015—Pigments exhibiting interference colours, e.g. transparent platelets of appropriate thinness or flaky substrates, e.g. mica, bearing appropriate thin transparent coatings
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2002/00—Crystal-structural characteristics
  • C01P2002/30—Three-dimensional structures
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
  • C01P2004/82—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases
  • C01P2004/84—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases one phase coated with the other
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
  • C09C2200/00—Compositional and structural details of pigments exhibiting interference colours
  • C09C2200/10—Interference pigments characterized by the core material
  • C09C2200/102—Interference pigments characterized by the core material the core consisting of glass or silicate material like mica or clays, e.g. kaolin
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
  • C09C2220/00—Methods of preparing the interference pigments
  • C09C2220/10—Wet methods, e.g. co-precipitation
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
  • C09C2220/00—Methods of preparing the interference pigments
  • C09C2220/10—Wet methods, e.g. co-precipitation
  • C09C2220/106—Wet methods, e.g. co-precipitation comprising only a drying or calcination step of the finally coated pigment

Definitions

• the invention relates to a process for preparing pearl luster pigments based on metal oxide coated mica flakes wherein, to coat with titanium dioxide in the rutile form, not only TiO 2 but also SnO 2 is precipitated onto the mica flakes in aqueous suspension and the pigment is then washed, dried and calcined.
• a very thin titanium dioxide layer is precipitated onto mica flakes followed alternatingly by at least one SnO 2 and TiO 2 layer, thicker layers being prepared by alternatingly precipitating a plurality of SnO 2 and TiO 2 layers.
• SnO 2 and TiO 2 layers are in each case prepared by slowly adding to the mica suspension, together with a base for keeping the pH constant, the tin salt solution with or without an oxidizing agent in the one case and the titanium salt solution in the other. In this way the precipitation can be very simply continued until the metal oxides are present in the desired layer thickness and consequently the pigment has the desired interference color.
• Customary washing, drying and calcining produces very brilliant pigments.
• a disadvantage is the very complicated process, in particular in the case of relatively thick layers.
• it requires relatively high tin dioxide contents, which in general range from about 5 to 7% by weight, based on the completed pigment.
• the thickness of the metal oxide layer and hence the interference color of the pigment is determined from the start by the amount of metal salt added. Corrections in the course of the coating process and in particular accurate end point determination as in the process of DE Patent No. 2,522,572 are not possible.
• the present invention accordingly provides a process for preparing pearl luster pigments based on metal oxide coated mica flakes wherein, to coat with titanium dioxide in the rutile form not only titanium dioxide but also tin dioxide is precipitated from aqueous metal salt solutions onto the mica flakes in aqueous suspension and the pigment is then washed, dried and calcined, which is characterized in that the precipitation of the tin dioxide is concluded before the addition of the titanium salt solution.
• this process gives a 100% rutilization in a very reliable manner even in the case of thick titanium dioxide layers even though only small amounts of tin need to be used. For instance, even an amount of about 0.25% by weight is sufficient. It is only to be on the safe side that in general a somewhat higher tin content of about 1% is preferred. However, these values are based on the weight of the mica used, so that the values based on the end product are still appreciably lower, depending on the amount of titanium dioxide precipitated on. It is also surprising that the amount of tin dioxide required for the process of rutilization is substantially independent of the particle size of the mica used.
• the mica suspension is brought to a suitable pH.
• a suitable pH range is from about 0.5 to 3, in particular from about 1.0 to 2.5.
• the range from about 1.5 to 2.0 has been found to be particularly advantageous.
• the tin salt solution is metered in together with a base, preferably at a temperature of about 50° C. to about 100° C.
• the tin salt used can in principle be any available divalent or tetravalent tin salt.
• SnCl 4 the pentahydrate producing particularly good coatings.
• the base with which the pH of the suspension is maintained substantially constant during the coating step is freely choosable in principle, so that for example alkali metal hydroxide solutions, in particular diluted sodium hydroxide solution, ammonium hydroxide or gaseous NH 3 or, if desired, even conventional buffer systems can be used, the contents of which can be easily determined by one of ordinary skill in the art.
• the coated mica pigments are then worked up in a conventional manner in that the pigment is separated off, washed, dried and then calcined. It has been found to be an advantage with the novel process that 100% rutilization is obtainable even under relatively mild calcination conditions. For instance, an approximately 30-minute calcination at about 850° C. or an equivalent time/temperature combination is sufficient. Compared with the prior art processes, where a time/temperature combination of 30 minutes/950° C. is customary, this further serves to keep the process simple and economical. Suitable equivalent time/temperature combinations may be determined conventionally according to known principles.
• the process described makes it possible to prepare any desired pigment with TiO 2 -layers of a thickness of up to 200 nm being reliably in the rutile modification
• the pigments possess diameters of 1-200 ⁇ m and thicknesses of about 0.1-5 ⁇ m, diameters of about 5-60 ⁇ m and thicknesses of about 0.5 ⁇ m being preferred, and can be used in all conventional applications.
• Example 1 is repeated, except that the titanium dioxide precipitation process is carried out at pH 1.8, pH 2.0 and pH 2.2 respectively.
• X-ray structure analysis shows that 100% rutilization is obtained.
• Example 1 is repeated, except that the temperature of the suspension is 90° C. and the titanium dioxide precipitation process is carried out at pH 1.6, pH 1.8 and pH 2.0 respectively. X-ray structure analysis shows that 100% rutilization is obtained.
• the pigments of Examples 1-7 have a composition conforming to 39.5% by weight of mica, 60.0% by weight of TiO 2 and 0.5% by weight of SnO 2 .
• Example 1 is repeated, except that the amount of tin salt is reduced to 1.5g of SnCl 4 ⁇ 5 H 2 O.
• the result obtained is a pigment of composition of 39.6% by weight of mica, 60.1% by weight of TiO 2 and 0.25% by weight of SnO 2 .
• X-ray analysis shows that 100% rutilization is obtained.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Pigments, Carbon Blacks, Or Wood Stains (AREA)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

Country Status (17)

Cited By (11)

Families Citing this family (25)

Citations (4)

• 1987
  • 1987-10-23 IN IN824/CAL/87A patent/IN169017B/en unknown
  • 1987-12-02 EP EP87117792A patent/EP0271767B1/de not_active Expired - Lifetime
  • 1987-12-02 ES ES198787117792T patent/ES2028035T3/es not_active Expired - Lifetime
  • 1987-12-02 DE DE8787117792T patent/DE3775017D1/de not_active Expired - Lifetime
  • 1987-12-10 HU HU875575A patent/HUT51658A/hu unknown
  • 1987-12-10 AU AU82414/87A patent/AU616874B2/en not_active Ceased
  • 1987-12-10 KR KR1019870014122A patent/KR960005171B1/ko not_active IP Right Cessation
  • 1987-12-10 BR BR8706699A patent/BR8706699A/pt not_active Application Discontinuation
  • 1987-12-11 ZA ZA879349A patent/ZA879349B/xx unknown
  • 1987-12-11 CA CA000554095A patent/CA1282649C/en not_active Expired - Fee Related
  • 1987-12-11 US US07/131,605 patent/US4867794A/en not_active Expired - Lifetime
  • 1987-12-11 CZ CS879087A patent/CZ279429B6/cs not_active IP Right Cessation
  • 1987-12-11 RU SU874203820A patent/RU2023715C1/ru active
  • 1987-12-11 MX MX009714A patent/MX168605B/es unknown
  • 1987-12-11 FI FI875461A patent/FI92598C/fi not_active IP Right Cessation
  • 1987-12-11 PL PL1987269418A patent/PL148533B2/pl unknown
  • 1987-12-11 JP JP62312417A patent/JP2598282B2/ja not_active Expired - Lifetime

Patent Citations (4)

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